Super-resolution optical recording medium on which information is recorded using train of prepits, optical recording medium reproduction device, and control method

ABSTRACT

A super-resolution optical recording medium includes: a medium information region on which medium identification information is recorded; a content region on which content information is recorded; and a blank region provided between the medium information region and the content region and in which at least two tracks are provided so as to connect a train of prepits in the medium information region and a train of prepits in the content region. No information is recorded on the blank region. Thus, a super-resolution optical recording medium is provided in which a region on which medium identification information is recorded and a region on which content information is recorded are different in track pitch and in which a reproduction error hardly occurs when reproduction shifts from the region on which the medium identification information is recorded to the region on which the content information is recorded.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of copending application U.S. Ser.No. 13/425,060 filed on Mar. 20, 2012, which is a continuation of U.S.Ser. No. 12/675,557 filed on Feb. 26, 2010, now U.S. Pat. No. 8,223,620,which is a National Phase filed under 35 USC 371 of internationalapplication PCT/JP2008/065376 filed on Aug. 28, 2008, which claimspriority to Japanese Application No. 2007-224836 filed on Aug. 30, 2007.

TECHNICAL FIELD

The present invention relates to a super-resolution optical recordingmedium on which information is recorded with the use of a train ofprepits including prepits shorter than a resolution limit of an opticalsystem of a reproduction device or a train of recording marks includingrecording marks shorter than the resolution limit of the optical systemof the reproduction device, the information being reproduced with theuse of a super-resolution technique. The present invention especiallyrelates to (i) a super-resolution optical recording medium (a) which canbe reproduced by a reproduction device which is also capable ofreproducing a normal optical recording medium on which information isrecorded with the use of a train of prepits which is constituted byprepits longer than the resolution limit of the optical system of thereproduction device and (b) in which a region where content informationis recorded has a small track pitch so that high recording density canbe realized, and (ii) a reproduction device which is capable ofreproducing both of the super-resolution optical recording medium andthe normal optical recording medium.

BACKGROUND ART

In recent years, there have been more opportunities to handleinformation having large data amount such as an image. On this account,it is necessary to increase recording density of an optical recordingmedium. In view of this, the following optical recording medium andsuper-resolution technique are proposed: (i) an optical recording mediumon which information is recorded with the use of prepits constituted byconcavity and/or convexity shorter than a resolution limit of an opticalsystem of a reproduction device and (ii) a super-resolution techniquefor reproducing the optical recording medium. Note that an opticalrecording medium reproduced with the use of the super-resolutiontechnique is hereinafter referred to as “super-resolution medium” or“super-resolution optical recording medium”, and a conventional opticalrecording medium, i.e., an optical recording medium which does notrequire use of the super-resolution technique and on which informationis recorded with the use of prepits longer than the resolution limit ofthe optical system of the reproduction device is hereinafter referred toas “normal medium” or “normal optical recording medium”. Further, notethat the resolution limit of the optical system is determined based on(i) a wavelength of a laser beam with which the reproduction deviceirradiates a medium and (ii) a numerical aperture of the optical system.

Examples of such a super-resolution medium include optical recordingmedia disclosed in Patent Literatures 1 and 2, respectively.

According to the super-resolution medium disclosed in Patent Literature1, a thermochromic layer whose optical properties such as transmissivityvaries depending on temperature is provided on a surface of a reflectinglayer on which surface laser beam is incident. In a case where thethermochromic layer is irradiated with a laser beam having certainpower, a super-resolution effect that a spot of the laser beam goes intoa pseudo-reduction state is produced. Thus, the thermochromic layerfunctions as a mask layer. Temperature distribution is caused in thespot on the mask layer due to light intensity distribution, andtransmissivity distribution is caused due to the temperaturedistribution. For example, in a case where the mask layer is made of amaterial whose transmissivity becomes higher as the temperature rises,only parts of the mask layer which have high temperature are high intransmissivity. Thus, the spot formed on the surface of the reflectinglayer is brought into the pseudo-reduction state. This allowsreproduction of a prepit shorter than a resolution limit of an opticalsystem. The technique disclosed in Patent Literature 1 can be appliednot only to a rewritable optical recording medium but also to aread-only optical recording medium.

Further, according to the super-resolution medium disclosed in PatentLiterature 2, a film layer (referred to as “function layer”) made of athin metal film or the like is provided on a substrate on whichinformation is recorded with the use of prepits which are concavitiesand/or convexities. At present, it is unknown how a super-resolutiontechnique used for the super-resolution medium of Patent Literature 2works. However, it is possible to reproduce a prepit shorter than theresolution limit of the optical system in a case where the temperatureof the function layer is changed by irradiating the function layer witha laser beam having higher power than usual.

CITATION LIST

-   Patent Literature 1-   Japanese Patent Application Publication, Tokukai, No. 2001-35012 A    (Publication Date: Feb. 9, 2001)-   Patent Literature 2-   Japanese Patent Application Publication, Tokukai, No. 2001-250274 A    (Publication Date: Sep. 14, 2001)

SUMMARY OF INVENTION

As described above, a super-resolution medium is irradiated by a laserbeam having high power. Such power of the laser beam is higher than thatof a laser beam with which a normal medium is irradiated.

Therefore, a super-resolution medium cannot be reproduced with the useof a reproduction device which is designed to reproduce a normal mediumsince such a reproduction device emits a laser beam having low power. Asa result, such a super-resolution medium is rejected as anirreproducible medium. Meanwhile, in a case where a normal medium ismistakenly loaded into a reproduction device which is designed toreproduce a super-resolution medium, such a normal medium may be brokendue to heat since such a reproduction device emits a laser beam havinghigh power. Alternatively, such a normal medium is rejected as anirreproducible medium since the super-resolution medium and the normalmedium are different not only in laser beam power but also in linearvelocity and clock.

In view of this, the inventors of the present invention devised asuper-resolution medium 105 (see FIGS. 13 and 14) in order to realize acompatible reproduction device which is capable of reproducing both of anormal medium and a super-resolution medium. The super-resolution medium105 includes a region 101 on which medium identification informationindicating that the super-resolution medium 105 is a super-resolutionmedium is recorded with the use of trains of prepits which are similarto those of a normal medium and which are away from one another by atrack pitch that is similar to that in the normal medium, i.e., recordedwith the use of trains of prepits which are spirally provided and eachof which is constituted by prepits longer than a resolution limit of anoptical system of a reproduction device. That is, the mediumidentification information can be reproduced with the use of a laserbeam having power suitable for a normal medium. Further, thesuper-resolution medium 105 includes a region 102 on which contentinformation is recorded with the use of trains of prepits which are awayfrom one another by a track pitch smaller than that in the region 101,which are spirally provided, and each of which includes prepits shorterthan the resolution limit of the optical system of the reproductiondevice.

As described above, according to the super-resolution medium 105, themedium identification information can be reproduced with the use of alaser beam having power suitable for a normal medium. This allowsrealization of a compatible reproduction device which is capable ofreproducing both of a normal medium and a super-resolution medium.Specifically, such a reproduction device irradiates a medium, which isloaded into the reproduction device, with a laser beam having powersuitable for a normal medium so as to read the medium identificationinformation, and then determines, based on the medium identificationinformation, whether the medium thus loaded is a normal medium or asuper-resolution medium. In a case where it is determined that themedium thus loaded is a normal medium, reproduction of contentinformation starts, whereas in a case where it is determined that themedium thus loaded is the super-resolution medium 105, the reproductiondevice switches to a light beam having power suitable for thesuper-resolution medium 105 before reproduction of content informationstarts.

However, unfortunately, a reproduction error tends to occur whenreproduction shifts from the region 101 to the region 102. This isbecause trains of prepits in the region 101 are provided so as to becontinuous with trains of prepits in the region 102, which is differentfrom the region 101 in track pitch, in order that the optical system ofthe reproduction device can move from the region 101 to the region 102while consecutively carrying out tracking servo control. The followingdescription deals with this problem with reference to FIG. 14. FIG. 14is an enlarged view of the interface between the region 101 and theregion 102.

Since the trains of prepits in the region 101 are provided so as to becontinuous with the trains of prepits in the region 102 as describedabove, a train of prepits a, which is adjacent to a train of prepits(train of prepits b) in the region 102, is provided in the region 101 soas to go around once. A track pitch between the train of prepits a andthe adjacent train of prepits in the region 102 is reduced from a trackpitch of the region 101 to a track pitch of the region 102 while thetrain of prepits a goes around once. That is, a track pitch between thetrain of prepits a and the train of prepits b is different from (i) atrack pitch between the train of prepits a and an adjacent train ofprepits in the region 101 and (ii) a track pitch between the train ofprepits b and an adjacent train of prepits in the region 102.

As in the region 101, the train of prepits b, which is adjacent to thetrain of prepits (the train of prepits a) in the region 101, is providedin the region 102 so as to go around once. A track pitch between thetrain of prepits b and the adjacent train of prepits in the region 101becomes larger from a track pitch of the region 102 to a track pitch ofthe region 101 while the train of prepits b goes around almost once.That is, as in the case of the train of prepits a, a track pitch betweenthe train of prepits a and the train of prepits b is different from (i)a track pitch between the train of prepits a and an adjacent train ofprepits in the region 101 and (ii) a track pitch between the train ofprepits b and an adjacent train of prepits in the region 102.

Consequently, reproduction of the train of prepits a is likely to beaffected by noise caused by the train of prepits b. Further, thetracking servo control is likely to become unstable when thereproduction device reads out the medium identification informationrecorded on the region 101, switches to laser beam power suitable for asuper-resolution medium, and then starts reproduction of the contentinformation recorded on the region 102. This is because (i) a trackpitch between the train of prepits a and the train of prepits b changeswhile the train of prepits a goes around once, and (ii) a track pitchbetween the train of prepits a and the train of prepits b is differentfrom (a) a track pitch between the train of prepits a and an adjacenttrain of prepits in the region 101 and (b) a track pitch between thetrain of prepits b and an adjacent train of prepits in the region 102.Such unstable tracking servo control causes a reduction in margin forexternal disturbances such as a tilt of the medium in a circumferentialdirection (tangential tilt), a tilt in a radial direction (radial tilt),and small fluctuation in laser beam power, thereby making thereproduction more likely to be affected by such external disturbances.Such external disturbances tend to cause a reproduction error.

The present invention was attained in view of the above problems, and anobject of the present invention is to realize (i) a super-resolutionoptical recording medium in which a region on which mediumidentification information is recorded and a region on which contentinformation is recorded are different in track pitch and in which areproduction error hardly occurs when reproduction shifts from theregion on which the medium identification information is recorded to theregion on which the content information is recorded, (ii) an opticalrecording medium reproduction device which is capable of reproducingboth of the super-resolution optical recording medium and a normaloptical recording medium, (iii) a control method of the opticalrecording medium reproduction device, (iv) a control program for theoptical recording medium reproduction device, and (v) acomputer-readable recording medium for storing the program.

In order to attain the above object, a super-resolution opticalrecording medium of the present invention includes: a first region onwhich medium identification information which causes a medium type to beidentified is recorded with use of trains of prepits each of which isconstituted by prepits longer than a resolution limit of an opticalsystem of an optical recording medium reproduction device; a secondregion on which content information is recorded with use of trains ofprepits each of which includes a prepit equal to or shorter than theresolution limit of the optical system, the second region having a trackpitch smaller than that of the first region; and a blank region providedbetween the first region and the second region so as to spirally connectthe trains of prepits in the first region and the trains of prepits inthe second region, the blank region including at least two tracks, atrack pitch, between (i) a first one of said at least two tracks that isadjacent to a first one of the trains of prepits of the first region and(ii) the first one of the trains of prepits, being identical to a trackpitch of the first region, a track pitch, between (i) a second one ofsaid at least two tracks that is adjacent to a second one of the trainsof prepits of the second region and (ii) the first one of the trains ofprepits which is on the first region side, changing into a track pitchof the second region, and a track pitch, between (i) the second one ofsaid at least two tracks and (ii) the second one of the trains ofprepits being identical to the track pitch of the second region, and noinformation being recorded on the blank region.

Note that, for convenience of description, the following descriptiondeals with a case where two tracks are provided in the blank region.Note also that, of the two tracks, a track adjacent to a train ofprepits in the first region is referred to as “a track A”, and a trackadjacent to a track of prepits in the second region is referred to as “atrack B”.

According to the arrangement, the medium identification informationrecorded on the first region is recorded with the use of a train ofprepits which is constituted by prepits longer than the resolution limitof the optical system of the optical recording medium reproductiondevice, i.e., the medium identification information recorded on thefirst region is recorded in a similar manner to a normal opticalrecording medium. This allows the medium identification information tobe reproduced with the use of a laser beam having power for a normaloptical recording medium. Therefore, the optical recording mediumreproduction device (i) irradiates a medium loaded into the opticalrecording medium reproduction device with a laser beam having powersuitable for a normal optical recording medium so as to read out themedium identification information, and then (ii) determines, based onthe medium identification information, whether the medium thus loaded isa normal optical recording medium or a super-resolution opticalrecording medium. Based on a result thus determined, the opticalrecording medium reproduction device can carry out processing inaccordance with the medium thus loaded (can change, for example, thepower of a laser beam in accordance with the medium thus loaded). Thisallows realization of a compatible reproduction device that is capableof reproducing both of a normal optical recording medium and thesuper-resolution optical recording medium.

According to the super-resolution optical recording medium, the contentinformation is recorded with the use of a train of prepits including aprepit equal to or shorter than the resolution limit of the opticalsystem. Further, the track pitch of the second region on which thecontent information is recorded is smaller than that of the firstregion. This allows realization of a super-resolution optical recordingmedium which has a storage capacity larger than a normal opticalrecording medium.

The super-resolution optical recording medium includes the blank regionin which the tracks A and B are provided so as to connect the train ofprepits in the first region and the train of prepits in the secondregion. Since the tracks A and B in the blank region is provided so asto be continuous with the train of prepits in the first region and thetrain of prepits in the second region, the optical system can smoothlymove from the first region to the second region while consecutivelycarrying out tracking servo control.

The track A is provided so as to be away, by a track pitch same as thatof the first region, from an adjacent train of prepits in the firstregion. This makes the reproduction of the first region less likely tobe affected by noise caused by the track A, thereby making it possibleto properly carry out tracking servo control.

A track pitch between the track B and the adjacent track A changes intothe track pitch of the second region. A track pitch between the track Band the adjacent train of prepits in the second region is same as thatof the second region. Although the tracking servo control becomesunstable during reproduction of the blank region, no reproduction erroroccurs since no information is recorded on the blank region. Duringreproduction of the track B, the tracking servo control can be stablycarried out with respect to the track pitch of the second region. Thus,reproduction of the second region starts. Further, the reproduction ofthe second region is less likely to be affected by noise caused by thetrack B, and the tracking servo control can be carried out properly.

As such, it is possible to realize a super-resolution optical recordingmedium in which a region on which medium identification information isrecorded and a region on which content information is recorded aredifferent in track pitch and in which a reproduction error hardly occurswhen reproduction shifts from the region on which the mediumidentification information is recorded to the region on which thecontent information is recorded.

Each of the tracks in the blank region may be (i) a train of prepits,(ii) a guide groove, or (iii) a combination of a train of prepits and aguide groove.

The super-resolution optical recording medium of the present inventionis preferably arranged such that first address information indicative ofa start position of the blank region is recorded on the first region,and second address information indicative of an end position of theblank region is recorded on the second region.

The super-resolution optical recording medium of the present inventionis preferably arranged such that address information of the blank regionis recorded on the first region.

According to the arrangement, the optical recording medium reproductiondevice (i) can recognize the position of the blank region so as to carryout proper processing (e.g. switch laser beam power of the opticalrecording medium reproduction device) with respect to the blank regionand the second region, and (ii) can cause the optical system toconsecutively jump to an adjacent track in the blank region so as tosmoothly shift to reproduction of the second region in a relativelyshort time period.

The super-resolution optical recording medium of the present inventionis preferably arranged such that address information of the secondregion is recorded on the first region.

According to the arrangement, the optical recording medium reproductiondevice (i) can recognize the position of the blank region and theposition of the second region so as to carry out proper processing (e.g.change laser beam power of the optical recording medium reproductiondevice) with respect to the blank region and the second region, and (ii)can cause the optical system to consecutively jump to an adjacent trackin the blank region so as to speedily access a starting position or adesired position of the second region and smoothly shift to reproductionof the second region in a relatively short time period.

The super-resolution optical recording medium of the present inventionis preferably arranged such that power information indicative of powerof a laser beam, with which the optical recording medium reproductiondevice irradiates the second region is recorded on the first region.

The super-resolution optical recording medium of the present inventionis preferably arranged such that the first region includes a test readregion where a train of prepits is provided, power of a laser beam withwhich the optical recording medium reproduction device irradiates thesecond region being adjusted with use of the train of prepits in thetest read region, and the train of prepits of the test read region isformed by a modulation method so as to have a linear recording density,the modulation method and the linear recording density being identicalto those of the trains of prepits in the second region.

According to the arrangement, the optical recording medium reproductiondevice can recognize laser beam power suitable for reproduction of thesecond region. This is because (i) power information indicative of powerof a laser beam with which the second region is irradiated is recordedon the super-resolution optical recording medium contains or (ii) thesuper-resolution optical recording medium includes a test read region inwhich a train of prepits is provided for adjusting power of the laserbeam with which the second region is irradiated. As such, it is possibleto produce a further effect that the content information recorded on thesecond region can be properly reproduced.

Further, since the test read region is provided in the first region, itis possible to produce an effect that a storage capacity of the secondregion is not sacrificed.

The super-resolution optical recording medium of the present inventionis preferably arranged such that blank power information indicative ofpower of a laser beam with which the optical recording mediumreproduction device irradiates the blank region is recorded on the firstregion.

According to the arrangement, in which blank power informationindicative of power of a laser beam with which the blank region isirradiated is recorded on the super-resolution optical recording medium,the optical recording medium reproduction device can recognize laserbeam power suitable for the blank region. This produces a further effectthat it is possible to properly carry out processing in the blankregion. Note that the laser beam power suitable for the blank region maybe smaller than that suitable for reproduction of the second region. Insuch a case, it is possible to reduce power consumption of the opticalrecording medium reproduction device. This is because the opticalrecording medium reproduction device can accurately recognize the laserbeam power suitable for the blank region based on the blank powerinformation.

In order to attain the above object, an optical recording mediumreproduction device of the present invention which is capable ofreproducing (i) a super-resolution optical recording medium and (ii) anormal optical recording medium on which various information is recordedwith use of trains of prepits each of which is constituted by prepitslonger than a resolution limit of an optical system of the opticalrecording medium reproduction device, the optical recording mediumreproduction device, includes: a reproducing section which reproducesinformation recorded on the super-resolution optical recording medium orthe normal optical recording medium, by (i) irradiating a desiredposition of the super-resolution optical recording medium or the normaloptical recording medium with reproduction light, and then (ii)converting, into an electric signal, light reflected from thesuper-resolution optical recording medium or the normal opticalrecording medium; a servo control section which carries out servocontrol in response to the electric signal; a content informationreproducing section which reproduces content information recorded on thesuper-resolution optical recording medium or the normal opticalrecording medium in response to the electric signal; and a controlsection which controls operations of the optical recording mediumreproduction device, the control section, including: an informationacquisition section which (i) reproduces and acquires mediumidentification information in response to an electric signal obtainedwhen the reproduction light is suitable for reproducing the normaloptical recording medium with use of reproduction light having powersuitable for reproduction of the normal optical recording medium, and(ii) acquires blank region information indicative of presence of a blankregion; a medium identification section which determines, based on themedium identification information, whether or not a super-resolutionoptical recording medium is loaded; and a blank control section whichcontrols the content information reproducing section based on the blankregion information so that the content information reproducing sectionstops an operation in the blank region.

In order to attain the above object, a method of the present inventionfor controlling an optical recording medium reproduction device which iscapable of reproducing (i) a super-resolution optical recording mediumand (ii) a normal optical recording medium on which various informationis recorded with use of trains of prepits each of which is constitutedby prepits longer than a resolution limit of an optical system of theoptical recording medium reproduction device, the method comprising thesteps of: reproducing information recorded on the super-resolutionoptical recording medium or the normal optical recording medium, by (i)irradiating a desired position of the super-resolution optical recordingmedium or the normal optical recording medium with reproduction light,and then (ii) converting into an electric signal light reflected fromthe super-resolution optical recording medium or the normal opticalrecording medium; carrying out servo control in response to the electricsignal; reproducing content information recorded on the super-resolutionoptical recording medium or the normal optical recording medium inresponse to the electric signal; and (i) reproducing and acquiringmedium identification information in response to an electric signalobtained when the reproduction light is suitable for reproducing thenormal optical recording medium with use of reproduction light havingpower suitable for reproduction of the normal optical recording medium,and (ii) acquiring blank region information indicative of presence of ablank region; determining, based on the medium identificationinformation, whether or not a super-resolution optical recording mediumis loaded; and controlling the content information reproducing sectionbased on the blank region information so that the content informationreproducing section stops an operation in the blank region.

According to the arrangement, the medium identification information isreproduced with the use of a laser beam having power suitable for anormal optical recording medium, and it is determined, based on themedium identification information, whether or not the super-resolutionoptical recording medium is loaded. Based on a result thus determined,the optical recording medium reproduction device can carry outprocessing in accordance with the optical recording medium (can changepower of a laser beam in accordance with the optical recording medium).Further, in a case where the optical recording medium reproductiondevice acquires blank region information indicative of presence of theblank region, the optical recording medium reproduction device continuesto carry out the servo control, but stops the reproduction of thecontent information in the blank region.

As such, it is possible to realize (i) a super-resolution opticalrecording medium in which a region on which medium identificationinformation is recorded and a region on which content information isrecorded are different in track pitch and in which a reproduction errorhardly occurs when reproduction shifts from the region on which themedium identification information is recorded to the region on which thecontent information is recorded, (ii) an optical recording mediumreproduction device which is capable of reproducing both of thesuper-resolution optical recording medium and a normal optical recordingmedium, and (iii) a control method of the optical recording mediumreproduction device.

The optical recording medium reproduction device of the presentinvention is preferably arranged such that said control section furtherincludes a power control section which, in a case where it is determinedby the medium identification section that the super-resolution opticalrecording medium is loaded, controls and changes power of thereproduction light of the reproducing section into one suitable forreproduction of a content region or into one suitable for reproductionof the blank region.

According to the arrangement, the optical recording medium reproductiondevice can change power of the reproduction light in accordance with theloaded optical recording medium. Further, the optical recording mediumreproduction device can change laser beam power into one suitable forthe blank region. This further produces an effect that the opticalrecording medium reproduction device can reproduce, in the bestcondition, the medium and regions (e.g. blank region and contentregion).

It is possible to cause a computer to function as the control section ofthe optical recording medium reproduction device based on a controlprogram for controlling the optical recording medium reproductiondevice. Further, it is possible to cause any computer to execute thecontrol program for controlling the optical recording mediumreproduction device by storing the control program in acomputer-readable recording medium.

A super-resolution optical recording medium of one of the presentinventions includes: a first region on which medium identificationinformation which causes a medium type to be identified is recorded withuse of trains of prepits each of which is constituted by prepits longerthan a resolution limit of an optical system of an optical recordingmedium reproduction device; a second region on which content informationis recorded with use of trains of prepits each of which includes aprepit equal to or shorter than the resolution limit of the opticalsystem, the second region having a track pitch smaller than that of thefirst region; and a blank region provided between the first region andthe second region so as to spirally connect the trains of prepits in thefirst region and the trains of prepits in the second region, the blankregion including at least two tracks, a track pitch, between (i) a firstone of said at least two tracks that is adjacent to a first one of thetrains of prepits of the first region and (ii) the first one of thetrains of prepits, being identical to a track pitch of the first region,a track pitch, between (i) a second one of said at least two tracks thatis adjacent to a second one of the trains of prepits of the secondregion and (ii) the first one of the trains of prepits which is on thefirst region side, changing into a track pitch of the second region, anda track pitch, between (i) the second one of said at least two tracksand (ii) the second one of the trains of prepits being identical to thetrack pitch of the second region, and no information being recorded onthe blank region.

As such, it is possible to realize a super-resolution optical recordingmedium in which a region on which medium identification information isrecorded and a region on which content information is recorded aredifferent in track pitch and in which a reproduction error hardly occurswhen reproduction shifts from the region on which the mediumidentification information is recorded to the region on which thecontent information is recorded.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating an external appearance of asuper-resolution optical recording medium of an embodiment of thepresent invention.

FIG. 2 is an enlarged view of a vicinity of a blank region of thesuper-resolution optical recording medium.

FIG. 3 is a cross-sectional view of the super-resolution opticalrecording medium.

FIG. 4 is a view illustrating an external appearance of asuper-resolution optical recording medium of another embodiment of thepresent invention.

FIG. 5 is an enlarged view of a vicinity of a blank region of thesuper-resolution optical recording medium shown in FIG. 4.

FIG. 6 is an enlarged view of a vicinity of a blank region of asuper-resolution optical recording medium of still another embodiment ofthe present invention.

FIG. 7 is an enlarged view of a vicinity of a blank region of asuper-resolution optical recording medium of still another embodiment ofthe present invention.

FIG. 8 is a cross-sectional view of the super-resolution opticalrecording medium shown in FIG. 7.

FIG. 9 is a block diagram illustrating an arrangement of an opticalrecording medium reproduction device of an embodiment of the presentinvention.

FIG. 10 is a block diagram illustrating an arrangement of a controlsection of the optical recording medium reproduction device.

FIG. 11 is a flow chart showing a flow of processing operation of theoptical recording medium reproduction device.

FIG. 12 is a flow chart showing a flow of processing operation of anoptical recording medium reproduction device of another embodiment ofthe present invention.

FIG. 13 is a view illustrating an external appearance of asuper-resolution optical recording medium.

FIG. 14 is an enlarged view of an interface between two regions of thesuper-resolution optical recording medium shown in FIG. 13, i.e., aregion on which medium identification information is recorded and aregion on which content information is recorded.

REFERENCE SIGNS LIST

-   -   1, 1 a, 1 b, 11: Medium information region (first region)    -   2, 2 a, 2 b, 12: Blank region    -   3, 3 a, 3 b, 13: Content region (second region)    -   1A, 1B, 11A: Test read region    -   10, 10 a, 10 b, 20, 105: Super-resolution optical recording        medium    -   26: Optical pickup (reproducing section)    -   31: Signal processing section (information acquisition section)    -   32: Medium identification section    -   33: Power control section    -   35: RF processing control section (blank control section)    -   36: Control section    -   37: Servo control section    -   39B: RF signal processing circuit (content information        reproducing section)    -   50, 50 a: Optical recording medium reproduction device

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described below with referenceto FIGS. 1 through 12. Note that the term “length of prepit” or the term“prepit length” used herein refers to a length of a prepit in atangential direction (in a direction normal to a radial direction of anoptical recording medium). Note also that an optical recording medium onwhich various kinds of information are recorded with the use of a trainof prepits constituted by prepits each longer than a resolution limit ofan optical system which is included in an optical recording mediumreproduction device (hereinafter referred to as “reproduction device”)of the present invention is referred to as “normal medium” or “normaloptical recording medium”.

Embodiment 1

An embodiment of a super-resolution optical recording medium of thepresent invention is described below with reference to FIGS. 1 through3. A super-resolution optical recording medium (hereinafter referred toas “super-resolution medium”) 10 of the present embodiment is areproduction-only medium, and is a super-resolution medium having across-sectional structure of a BD (Blu-ray Disc) type. According to thepresent embodiment, an optical system of a reproduction device has thefollowing particulars: a laser wavelength is 405 nm, a numericalaperture of a converging lens is 0.85, and a resolution limit is 119 nm.Note that the characteristics of each semiconductor laser, which isoperated in conformity with a standard such as a BD standard, vary fromsemiconductor laser to semiconductor laser due to their manufacturingprocess. On this account, in a case where a laser beam is describedherein as having a laser wavelength of 405 nm, it means that the laserbeam has a laser wavelength which falls in a range from 400 nm to 410nm.

FIG. 1 is a view illustrating an external appearance of thesuper-resolution medium 10.

The super-resolution medium 10 includes a medium information region(first region) 1 on which medium information is recorded, a contentregion (second region) 3 on which content information such as video andsoftware is recorded, and a blank region 2 provided between the mediuminformation region 1 and the content region 3.

FIG. 2 is an enlarged view of a vicinity of the blank region 2.

The medium information is recorded, in conformity with the BD standard,on the medium information region 1 with the use of a train of prepitswhich is provided in a spiral manner and which is constituted by prepitsand spaces which mainly have a length of 149 nm, 223.5 nm, 298 nm, 372.5nm, 496 nm, 570.5 nm or 645 nm. Each of the prepits and spaces is longerthan 119 nm which is the resolution limit of the optical system of thereproduction device. A track pitch is 320 nm in the medium informationregion 1.

The medium information recorded on the medium information region 1includes information such as (i) medium identification information whichindicates that a recording mode of the content region 3 is asuper-resolution recording mode and which causes medium type of thesuper-resolution medium 10 to be identified, (ii) reproduction clockswitching information which causes the reproduction device to switch toa reproduction clock, and (iii) address of recorded information.

As shown in FIG. 2, the medium information region 1 further includes atest read region 1A in which a train of prepits is provided foradjusting (setting) power of a laser beam with which the content region3 is irradiated. Note that such laser beam power adjusted by use of thetest read region 1A is equal to that of a laser beam with which theblank region 2 is irradiated.

The train of prepits in the test read region 1A contains a prepit thatis identical to the shortest prepit in the content region 3, and isconstituted only by prepits which are equal in length to those of thecontent region 3. The train of prepits in the test read region 1A formsa random pattern which is in conformity with a prepit width of thecontent region 3 and a modulation method of the content region 3. Thetrain of prepits, having a length which corresponds to reference data,is provided in the test read region 1A so as to have a linear recordingdensity identical to that of the content region 3. Further, the train ofprepits of the test read region 1A can be provided in any region of themedium information region 1. Further, in a case where super-resolutionmedia are the same in reference data, the reference data can be recordedin the reproduction device or can be recorded in a region other than thetest read region 1, which region is in the medium information region 1.

The blank region 2 functions as a guide in a case where the reproductiondevice causes the optical system to move from the medium informationregion 1 to the content region 3 while carrying out tracking servocontrol. Further, A train of prepits is provided in the blank region 2in which train of prepits having a length of 149 nm is spirally providedat regular intervals so as to spirally connect the train of prepits ofthe medium information region 1 and the train of prepits of the contentregion 3. Note that the train of prepits is provided so as to spirallygo around at least twice in the blank region 2. In the presentembodiment, the train of prepits is provided so as to spirally go aroundtwice in the blank region 2. Note also that no information to bereproduced such as medium information and content information isrecorded on the train of prepits in the blank region 2.

A depth of each of the prepits of the blank region 2 is not limited to aspecific one, provided that such a depth allows the optical system ofthe reproduction device to detect a tracking error signal. A depth ofapproximately 65 nm which is in conformity with the BD standard causesno problem, in a case where a laser wavelength of the optical system ofthe reproduction device is 405 nm and the numerical aperture NA of theconverging lens is 0.85, as with the present embodiment. The blankregion 2 will be described later in detail.

The content information is recorded on the content region 3 with the useof a train of prepits, by spirally providing the train of prepits inwhich prepits and spaces are combined whose length is mainly 116 nm, 174nm, 232 nm, 290 nm, 348 nm, 406 nm or 464 nm. That is, the train ofprepits contains a prepit and a space whose length is 116 nm that issmaller than 119 nm that is the resolution limit of the optical systemof the reproduction device. A track pitch in the content region 3 is 260nm that is smaller than the track pitch in the medium information region1. The content region 3 has a storage capacity which is around 1.6 timeslarger than that of a normal medium of BD type. Note that the storagecapacity is calculated back based on the shortest prepit length and thetrack pitch.

FIG. 3 is a cross-sectional view of the super-resolution medium 10.

The super-resolution medium 10 is arranged such that (i) a reflectinglayer 5 and a super-resolution function layer 6 which causes asuper-resolution effect are stacked, in this order by sputtering, on asubstrate 4 on which the prepits of each of the regions are provided and(ii) a cover layer 7 having translucency is provided on thesuper-resolution function layer 6.

The substrate 4 has a thickness of approximately 1.1 mm, and is made ofpolycarbonate. The reflecting layer 5 is a silicon layer having athickness of 7 nm, and the super-resolution function layer 6 is a zincoxide layer having a thickness of 155 nm. The cover layer 7 has athickness of approximately 0.1 mm, and is made of polycarbonate. Notethat the prepits of each of the regions are provided on the substrate 4so as to have concave shape and/or convex shape.

In a case where the content region 3 is irradiated by a laser beamhaving power suitable for reproduction of the content region 3, heat isgenerated by the reflecting layer 5. The heat causes a light intensitydistribution within a laser spot, which distribution causes temperaturedistribution. This ultimately causes optical transmittance distributionwithin the laser spot on the super-resolution function layer 6. As aresult, the laser spot goes into a pseudo-reduction state. This allows areproduction of the train of prepits in the content region 3, whichtrain of prepits includes prepits shorter than the resolution limit ofthe optical system of the reproduction device, thereby making itpossible to deal with more information than a normal medium. Note thatthe super-resolution function layer 6 is not limited to a specificstructure, provided that the train of prepits in the content region 3can be reproduced. The super-resolution function layer 6 can be a masklayer disclosed in Patent Literature 1 or a function layer disclosed inPatent Literature 2, for example. Note also that (i) the laser lightpower suitable for reproduction of the content region 3 is approximately1.0 mW and (ii) laser light power suitable for reproduction of themedium information region 1 is approximately 0.3 mW which is the same aslaser light power suitable for reproduction of a normal medium.

Further, the medium identification information recorded on the mediuminformation region 1 can be reproduced with the use of a laser beamhaving power for the normal medium. This is because the mediumidentification information is recorded with the use of a train ofprepits which is constituted by prepits longer than the resolution limitof the optical system of the reproduction device, i.e., the mediumidentification information is recorded in a similar manner to a normalmedium. Therefore, the reproduction device (i) irradiates a medium,which is loaded into the reproduction device, with a laser beam havingpower for a normal medium so as to read out the medium identificationinformation, and then (ii) determines, based on the mediumidentification information, whether the medium thus loaded is a normalmedium or a super-resolution medium. Based on a result thus determined,the reproduction device can carry out processing in accordance with themedium thus loaded (can change, for example, the power of a laser beamin accordance with the medium thus loaded). This allows realization of acompatible reproduction device that is capable of reproducing both of anormal medium and the super-resolution medium 10.

The following description deals with the blank region 2 in more detailwith reference to FIG. 2. Note that, for convenience of description, atrain of prepits in the medium information region 1, which train ofprepits is adjacent to the blank region 2, is referred to as “a train ofprepits a”, and a train of prepits in the content region 3 which trainof prepits is adjacent to the blank region 2 is referred to as “a trainof prepits b”. Of the inner circumferential train of prepits and theouter circumferential train of prepits in the blank region 2, a train ofprepits adjacent to the train of prepits a of the medium informationregion 1 is referred to as “a train of prepits A”, and a train ofprepits adjacent to the train of prepits b of the content region 3 isreferred to as “a train of prepits B”.

The train of prepits A of the blank region 2 is provided so as to beaway, by a track pitch of 320 nm (by the track pitch of the mediuminformation region 1), from the adjacent train of prepits a. The trainof prepits B is provided so that a track pitch between the train ofprepits B and the adjacent train of prepits A (the train of prepits on afirst region side of the blank region 2) is reduced to 260 nm (the trackpitch of the content region 3) from 320 nm while the train of prepits Bgoes around. The train of prepits B is provided so as to be away, by ata track pitch of 260 nm, from the adjacent train of prepits b.

Since the train of prepits A is provided so as to be away, by the trackpitch of the medium information region 1, from the adjacent train ofprepits a, a track pitch, on an identical radius within the mediuminformation region 1, between the adjacent trains of prepits is equal toeach other irrespective of the inner train of prepits or the outer trainof prepits. Since, during the reproduction, (i) the medium informationregion 1 is less affected by noise caused by adjacent trains of prepitsand (ii) the tracking servo control is appropriately carried out, thereoccurs no increase in reproduction error.

Further, since the train of prepits B is provided so that a track pitchbetween the train of prepits B and the adjacent train of prepits A isreduced to the track pitch of the content region 3 from the track pitchof the medium information region 1, the tracking servo control can bestably carried out with respect to the track pitch in the content region3.

The tracking servo control tends to become unstable in the blank region2 since (i) a track pitch between the train of prepits A and the trainof prepits B is different from (a) a track pitch between the train ofprepits A and the adjacent train of prepits a and (b) a track pitchbetween the train of prepits B and the adjacent train of prepits b and(ii) a track pitch between the train of prepits A and the train ofprepits B changes while the train of prepits A and the train of prepitsB go around.

Therefore, if the blank region 2 contains information to be reproducedsuch as medium information and content information, such unstabletracking servo control causes a reduction in margin for externaldisturbances such as a tilt of the medium in a circumferential direction(tangential tilt), a tilt of the medium in a radial direction (radialtilt), and a small fluctuation in laser beam power, thereby making thereproduction error more likely to occur.

However, no reproduction error occurs since no information to bereproduced such as medium information and content information isrecorded on the blank region 2, as described above.

Further, the train of prepits B is provided so as to be away, by thetrack pitch of the content region 3, from the adjacent train of prepitsb. This allows the reproduction of the content region 3 to be lessaffected by noise which is caused by an adjacent train of prepits,thereby making it possible to properly carry out the tracking servocontrol. As a result, there is no increase in reproduction error.

In this manner, the provision of the blank region 2 allows properreproductions of the medium information region 1 and the content region3 without causing an increase in reproduction error, although the mediuminformation region 1 and the content region 3 are different in recordingmode and track pitch. This allows the super-resolution medium 10 to havelarger storage capacity than a normal medium, and to be reproduced in asingle reproduction device which can reproduce a normal medium.

Further, there is no rapid change in track pitch because of the presenceof the blank region 2. This produces a further effect, duringmanufacturing of a master disc, that it is possible to more easilycontrol a speed at which a slider, provided in an exposure apparatus, ismoved in a radial direction. This is described below in detail.

The exposure apparatus used in manufacturing the master disc includes(i) a laser light source, (ii) a stage for fixing and rotating asubstrate on which a photoresist layer is deposited, and (iii) a sliderhaving components such as a lens for converging a laser beam onto thephotoresist layer provided on the substrate (the laser light source andthe slider can integrally move). The stage on which the substrate isfixed is rotated, exposure is carried out while the slider is beingmoved in the radial direction with respect to the center of the rotationof the stage, and then development is carried out. This allowsproduction of a spiral shaped pattern of trains of prepits and/or apattern of guide grooves. In a case where the medium information region1 and the content region 3 which are different in track pitch areadjacently provided, it becomes difficult to control the speed at whichthe slider is moved in the radial direction, thereby causing a deviationfrom a desired radius position. This is because it is necessary to makea rapid change in the speed at which the slider is moved in the radialdirection so as to respond to a change in track pitch. However, in acase where the blank region 2 is provided as in the Embodiment 1, it ispossible to reduce a change in the speed at which the slider is moved inthe radial direction. Because this gives rise to easier control of theslider, it becomes less likely to cause a deviation from the desiredradial position.

The super-resolution medium 10 thus described is a suitable example, andcan be modified as follows, for example.

The reflecting layer 5 can be made of a material such as aluminum,silver, gold, Ge or their mixture, provided that sufficient amount ofreflection can be obtained. Further, the super-resolution function layer6 can be made of a material such as CeO₂, TiO₂, GeSbTe or AgInSbTe.Further, the cover layer 7 can be prepared by a method such as a methodof bonding a film with the use of a UV cured resin or by a spin coatmethod.

Further, the blank region 2 is not limited in particular, provided that(i) the optical system of the reproduction device can move whilecarrying out tracking, and (ii) the blank region 2 includes a prepit ofnot less than the shortest prepit of the trains of prepits in thecontent region 3. Further, the prepits in the blank region 2 can be notless than two types of prepits, having respective different lengths,which are randomly provided so as not to comply with any signalmodulation method of an optical recording medium. This is because noinformation to be reproduced such as medium information or contentinformation is recorded on the blank region 2.

The present embodiment has dealt with a case where the mediuminformation region 1 is provided in the innermost part of thesuper-resolution medium 10. However, the medium information region 1 canbe provided in an outer circumferential part of the super-resolutionmedium 10 or can be provided in an inner circumferential part and in theouter circumferential part of the super-resolution medium 10, providedthat the blank region 2 is provided between the medium informationregion 1 and the content region 3.

The present embodiment has dealt with a case where the mediuminformation region 1 includes the test read region 1A. However, anotherarrangement is possible in which (i) the medium information region 1includes, instead of the test read region 1A, a region, on which powerinformation indicative of power of a laser beam with which the contentregion 3 is irradiated, is recorded, and (ii) the reproduction devicereproduces the power information so as to recognize power of a laserbeam suitable for reproduction of the content region 3. Further, in acase where a plurality of super-resolution media are the same in laserbeam power suitable for reproduction of the content region, such laserbeam power can be recorded in the reproduction device instead ofproviding the test read region 1A.

Further, for example, the medium information region 1 can includeseveral regions that are different in track pitch so that testreproduction of a super-resolution medium can be carried out.

Further, a super-resolution optical recording medium of the presentinvention is not limited to the one thus described, and can be arecordable super-resolution optical recording medium. For example, thesuper-resolution optical recording medium may be arranged so as toinclude a first region (medium information region) in which tracks eachconstituted by wobbles (meandering guide grooves) are provided, and asecond region on which content information is recorded with the use ofrecording marks and spaces. Similar effects can be obtained even in sucha super-resolution optical recording medium in a case where the blankregion on which no information is recorded is provided. In this case, itis only necessary that tracks in the blank region each of which tracksis constituted by wobbles be provided so as to connect the tracks in thefirst region and the tracks in the second region. Since mediumidentification information can be recorded on the first region on thebasis of a cycle of the wobbles or the like, information indicating (i)that the blank region is present and (ii) that no information isrecorded on the blank region can be recorded on the first region.

With this arrangement, the optical system of the reproduction device cansmoothly move from the first region to the second region whileconsecutively carrying out tracking servo control. Further, even if thetracking servo control becomes unstable in the blank region, suchunstable tracking servo control causes no reproduction error since noinformation is recorded on the blank region. This allows realization ofa recordable super-resolution optical recording medium (i) whichincludes a first region and a second region which has a track pitchsmaller than that of the first region, and (ii) in which a reproductionerror is hard to occur when reproduction shifts from the first region tothe second region. Thus, the present invention can be applied not onlyto a reproduction only BD-ROM (Blu-ray Disc Read Only Memory), but alsoto a recordable BD-R (Blu-ray Disc Recordable) and a BD-RE (Blu-ray DiscRewritable).

Further, tracks in each of the first region, the second region, and theblank region are not limited to wobbles. Each of the tracks in the firstregion and the blank region may be arranged so as to include prepitsand/or guide grooves as in the reproduction-only medium of theEmbodiment 1, and each of the tracks in the second region may bearranged so as to include guide grooves.

Embodiment 2

Another embodiment of a super-resolution medium of the present inventionis described below with reference to FIGS. 4 and 5. For convenience ofdescription, constituents which have identical functions to those of theEmbodiment 1 are given identical reference numerals, and are notexplained repeatedly. Basically, the following description deals withdifferences from the super-resolution medium 10 of the Embodiment 1.

FIG. 4 is a view illustrating an external appearance of asuper-resolution medium 10 a of the present embodiment.

The super-resolution medium 10 a includes a medium information region(first region) 1 a on which medium information is recorded, a contentregion (second region) 3 a on which content information such as video orsoftware is recorded, and a blank region 2 a provided between the mediuminformation region 1 a and the content region 3 a.

FIG. 5 is an enlarged view of a vicinity of the blank region 2 a.

The medium information region 1 a is different from the mediuminformation region 1 of the super-resolution medium 10 in that firstaddress information indicative of a starting position of the blankregion 2 a is additionally recorded. The content region 3 a is differentfrom the content region 3 of the super-resolution medium 10 in thatsecond address information indicative of an end position of the blankregion 2 a is additionally recorded.

In a case where such address information indicative of a position of theblank region 2 a is recorded as described above, the reproduction device(i) can recognize the position of the blank region 2 a so as to carryout proper processing (e.g. change laser beam power of the reproductiondevice) (see Embodiments 5 and 6 for details) with respect to the blankregion 2 a and the content region 3 a, and (ii) can cause the opticalsystem to consecutively jump to an adjacent track in the blank region 2a so as to smoothly shift to reproduction of the content region 3 a in arelatively short time period.

The medium information region 1 a includes a test read region 1B insteadof the test read region 1A. A train of prepits in the test read region1B includes a prepit that is identical to the shortest prepit of thecontent region 3 a, and is constituted only by prepits whose lengths areequal to those of the content region 3. The train of prepits in the testread region 1 B forms a random pattern which is in conformity with aprepit width of the content region 3 a and a modulation method of thecontent region 3 a. The train of prepits having a length whichcorresponds to reference data is provided in the test read region 1B soas to have a linear recording density identical to that of the contentregion 3. The train of prepits in the test read region 1B can beprovided in any region of the medium information region 1 a. Accordingto the present embodiment, the train of prepits in the test read region1B is provided in a track in the medium information region 1 a whichtrack is adjacent to the blank region 2 a. Note that the reference datacan be recorded in the reproduction device or can be recorded in aregion other than the test read region 1B which region is in the mediuminformation region 1 a in a case where super-resolution media are thesame in reference data.

The blank region 2 a is different from the blank region 2 of thesuper-resolution medium 10 in that guide grooves are used instead of thetrain of prepits in the blank region 2. A guide groove is provided inthe blank region 2 a so as to spirally go around at least twice in theblack region 2 a. In the present embodiment, a guide groove is providedso as to spirally go around four times in the blank region 2 a. A depthof each of the guide grooves in the blank region 2 a is not limited to aspecific one, provided that such a depth allows an optical system of areproduction device to detect a tracking error signal. A depth ofapproximately 65 nm which is in conformity with BD standard causes noproblem in a case where (i) the optical system of the reproductiondevice has a laser wavelength of 405 nm, and (ii) numerical aperture NAof a converging lens is 0.85 as in the present embodiment.

The following description deals with the blank region 2 a in moredetail. For convenience of description, among the four guide grooves inthe blank region 2 a, a guide groove that is adjacent to a train ofprepits a in the medium information region 1 a is hereinafter referredto as “a guide groove C”, and a guide groove that is adjacent to theguide groove C is hereinafter referred to as “a guide groove D”.Further, of the guide grooves adjacent to the guide groove D, a guidegroove that is nearer to the content region 3 a is hereinafter referredto as “a guide groove E”, and a guide groove that is adjacent to theguide groove E and the train of prepits b in the content region 3 a ishereinafter referred to as “a guide groove F”.

The guide groove C in the blank region 2 a is provided so as to be away,by a track pitch of 320 nm (by a track pitch of the medium informationregion 1 a), from the adjacent train of prepits a. A track pitch betweenthe guide grooves C and D is smaller by approximately 18 nm than thatbetween the train of prepits a and the guide groove C, and a track pitchbetween the guide grooves D and E is smaller by approximately 18 nm thanthat between the guide grooves C and D, and a track pitch between theguide grooves E and F is smaller by approximately 18 nm than thatbetween the guide grooves D and E. Consequently, the guide groove F isaway from the adjacent guide groove E by a track pitch of approximately260 nm (by a track pitch of the content region 3 a). Further, the guidegroove F is away from the adjacent train of prepits b by a track pitchof 260 nm.

The blank region 2 a provided in this manner allows proper reproductionof the medium information region 1 a and the content region 3 a withoutcausing an increase in reproduction error, although the mediuminformation region 1 a and the content region 3 a are different inrecording mode and track pitch. This allows the super-resolution medium10 a to have larger storage capacity than a normal medium, and to bereproduced in a single reproduction device which can also reproduce anormal medium.

Since the four guide grooves are provided in the blank region 2 a, theblank region 2 a is larger than the blank region 2 of the Embodiment 1.This allows a reduction in amount of change in track pitch per unitlength in a radial direction. As such, it is possible to more easilycontrol speed at which a slider is moved in a radial direction in anexposure step during manufacturing a master disc, thereby making adeviation from a desired radius position less likely to occur.

Further, the optical system of the reproduction device can carry outtracking servo control more stably while traveling through the blankregion 2 a. This allows an increase in margin for external disturbancesand the like. As such, the optical system can more smoothly move fromthe medium information region 1 a to the content region 3 a.

In a case where it is desired that storage capacity be secured as muchas possible in a super-resolution medium, it is only necessary to makethe blank region as small as possible, for example, by causing the guidegroove in the blank region to go around twice as in the Embodiment 1.Further, at a certain position in a circumferential direction, a trackpitch between adjacent trains of prepits or guide grooves may becomesmaller as a distance from an inner periphery becomes larger.Specifically, such a track pitch may become smaller as follows as adistance from an inner periphery becomes larger: 320 nm, approximately310 nm, approximately 280 nm, approximately 270 nm, approximately 265nm, 260 nm. This makes it easier to manufacture a master disc of anoptical recording medium. That is, in a case where an amount of changein speed at which a slider is moved in a radial direction of the masterdisc becomes smaller from a certain point as above, the speed at whichthe slider is moved tends to become stable when a track pitch between atrain of prepits or a guide groove and an adjacent train of prepits orguide groove on an inner periphery side is 260 nm.

The super-resolution medium 10 a thus described is a suitable example,and can be modified as described in the Embodiment 1 or can be modifiedas follows, for example.

The present embodiment has dealt with a case where the addressinformation of the blank region 2 a is recorded on each of the mediuminformation region 1 a and the content region 3 a, but does not intendto limit to this. Such address information may be recorded on the mediuminformation region 1 a in a different information state, for example.

Alternatively, the medium information region 1 a may contain, instead ofthe address information of the blank region 2 a, address informationindicative of location of the content region 3 a. In a case where theaddress information of the content region 3 a is recorded on the mediuminformation region 1 a, the reproduction device (i) can recognize theposition of the blank region 2 a and the content region 3 a so as tocarry out proper processing (e.g. change laser beam power of thereproduction device) (see Embodiments 5 and 6 for details) with respectto the blank region 2 a and the content region 3 a, and (ii) can causethe optical system to consecutively jump to an adjacent track in theblank region 2 so as to speedily access a starting position or a desiredposition of the content region 3 a and smoothly shift to reproduction ofthe content region 3 a in a relatively short time period.

The present embodiment has dealt with a case where the mediuminformation region 1 a includes the test read region 1B. However,another arrangement is possible in which (i) the medium informationregion 1 a includes, instead of the test read region 1B, a region, onwhich power information indicative of power of a laser beam with whichthe content region 3 a is irradiated, is recorded, and (ii) thereproduction device reproduces the power information so as to recognizepower of a laser beam suitable for reproduction of the content region 3a. Further, the test read region 1B may be substituted by a test readregion 11A of Embodiment 4 later described. Further, in a case where aplurality of super-resolution media are the same in laser beam powersuitable for reproduction of the content region, such laser beam powercan be recorded in the reproduction device instead of providing the testread region 1B.

A train of prepits can be provided in the blank region 2 a so as tospirally go around at least twice as in the Embodiment 1. Alternatively,a train of prepits and guide groove can be provided in the blank region2 a so as to spirally go around at least twice as in the Embodiment 3described below.

Embodiment 3

Another embodiment of a super-resolution medium of the present inventionis described below with reference to FIG. 6. For convenience ofdescription, constituents which have identical functions to those of theEmbodiment 2 are given identical reference numerals, and are notexplained repeatedly. Basically, the following description deals withdifferences from the super-resolution medium 10 a of the Embodiment 2.

FIG. 6 is an enlarged view of a vicinity of a blank region 2 b of asuper-resolution medium 10 b of the present embodiment.

The medium information region 1 b is different from the mediuminformation region 1 a of the super-resolution medium 10 a in that blankpower information indicative of power of a laser beam with which theblank region 2 b is irradiated is additionally recorded. Thereproduction device reproduces the blank power information so as torecognize power of a laser beam suitable for blank region 2 b. Note thatthe laser beam power suitable for the blank region 2 b may be smallerthan that suitable for reproduction of the content region 3 b. In such acase, it is possible to reduce power consumption of the reproductiondevice since the reproduction device can accurately recognize the laserbeam power suitable for the blank region 2 b based on the blank powerinformation.

The content region 3 b is arranged in a similar manner to the contentregion 3 a of the super-resolution medium 10 a.

The blank region 2 b is different from the blank region 2 a of thesuper-resolution medium 10 a in that a combination of a train of prepitsand a guide groove is used instead of the guide grooves. The train ofprepits and guide groove are provided in the blank region 2 b so as tospirally go around at least twice. In the present embodiment, the trainof prepits and guide groove are provided in the blank region 2 b so asto spirally go around four times. A track pitch in the blank region 2 bis similar to that in the blank region 2 a. Further, the train ofprepits in the blank region 2 b is similar to that in the blank region2. Specifically, the train of prepits in the blank region 2 b includesprepits each of which has a length of 149 nm and which are disposed atregular intervals. Further, the guide groove in the blank region 2 b issimilar to that in the blank region 2 a.

As in the Embodiments 1 and 2, the blank region 2 b provided in thismanner allows proper reproduction of the medium information region 1 band the content region 3 b without causing an increase in reproductionerror, although the medium information region 1 b and the content region3 b are different in recording mode and track pitch. This allows thesuper-resolution medium 10 b to have larger storage capacity than anormal medium, and to be reproduced in a single reproduction devicewhich can reproduce a normal medium.

Embodiment 4

Another embodiment of a super-resolution medium of the present inventionis described below with reference to FIGS. 7 and 8. A super-resolutionmedium 20 of the present embodiment is a reproduction only medium and isa super-resolution medium having a cross-section structure of HD_DVD(High Definition Digital Versatile Disc) type. According to the presentembodiment, an optical system of a reproduction device has the followingparticulars: a laser wavelength is 405 nm, a numerical aperture of aconverging lens is 0.65, and a resolution limit of the optical system is156 nm.

The super-resolution medium 20 includes a medium information region(first region) 11 on which medium information is recorded, a contentregion (second region) 13 on which content information such as video orsoftware is recorded, and a blank region 12 provided between the mediuminformation region 11 and the content region 13.

FIG. 7 is an enlarged view of a vicinity of the blank region 12.

The medium information is recorded, in conformity with the HD_DVDstandard, on the medium information region 11 with the use of a train ofprepits which is provided in a spiral manner and which is constituted byprepits and spaces, the shortest prepit having a length of 204 nm. Notethat each of the prepits and spaces in the train of prepits longer than156 nm which is the resolution limit of the optical system of thereproduction device. Further, note that a track pitch in the mediuminformation region 11 is 400 nm.

The medium information recorded on the medium information region 11includes information such as (i) medium identification information whichindicates that the content region 13 is recorded in a super-resolutionrecording mode and which causes medium type of the super-resolutionmedium 20 to be identified, (ii) reproduction clock switchinginformation which causes the reproduction device to switch to areproduction clock, (iii) information indicative of address of therecorded information, and (iv) first address information indicative of astarting position of the blank region 12.

As shown in FIG. 7, the medium information region 11 includes a testread region 11A in which a train of prepits is provided for adjusting(setting) power of a laser beam with which the reproduction deviceirradiates the content region 13. Note that such laser beam poweradjusted by use of the test read region 11A is equal to that of a laserbeam with which the blank region 12 is irradiated.

The train of prepits in the test read region 11A contains a prepit thatis identical to the shortest prepit of the content region 13, and isconstituted only by prepits whose lengths are equal to those of theprepits of the content region 13. The train of prepits in the test readregion 11A forms a random pattern which is in conformity with a prepitwidth of the content region 13 and a modulation method of the contentregion 13. The train of prepits having a length which corresponds toreference data are provided in the test read region 11A so as to have alinear recording density identical to that in the content region 13.Each time a medium is loaded into a reproduction device, a train ofprepits having a length which corresponds to the reference data israndomly selected so that test read can be carried out. The train ofprepits in the test read region 11A can be provided in any region of themedium information region 11. Further, in a case where super-resolutionmedia are the same in reference data, the reference data can be recordedin the reproduction device or can be recorded in a region other than thetest read region 11A, which region is in the medium information region11.

Since the test read is carried out while laser beam power is beingchanged, a train of prepits may be irradiated with a laser beam havingpower larger than that suitable for the content region 13. In a casewhere there is only one train of prepits having a length whichcorresponds to the reference data, a medium is likely to be damagedsince the only one train of prepits is repeatedly irradiated with thelaser beam. In view of this, a plurality of trains of prepits eachhaving a length which corresponds to the reference data are provided asdescribed above so that it is possible to prevent the medium from beingdamaged.

The blank region 12 serves as a guide in a case where the reproductiondevice causes the optical system to move from the medium informationregion 11 to the content region 13 while carrying out tracking servocontrol. The train of prepits in the blank region 12 is spirallyprovided so as to spirally connect the train of prepits in the mediuminformation region 11 and the train of prepits in the content region 13.The train of prepits in the blank region 12 is arranged such that aprepit having a length of 204 nm, a space having a length of 204 nm, aprepit having a length of 408 nm, and a space having a length of 408 nmare repeatedly provided in this order. The train of prepits in the blankregion 12 is provided so as to spirally go around at least twice. In thepresent embodiment, the train of prepits in the blank region 12 isprovided so as to spirally go around four times. Further, no informationto be reproduced such as medium information or content information isrecorded on the blank region 12.

Further, a depth of each of the prepits in the blank region 12 is notlimited to a specific one, provided that such a depth allows the opticalsystem of the reproduction device to detect a tracking error signal. Adepth of approximately 78 nm causes no problem in a case where a laserwavelength of the optical system of the reproduction device is 405 nm,and the numerical aperture of the converging lens is 0.65. The blankregion 12 is described later in detail.

The content information is recorded on the content region 13 with theuse of a train of prepits which is provided in a spiral manner and whichincludes prepits and spaces smaller than 156 nm which is the resolutionlimit of the optical system of the reproduction device, the shortestprepit having a length of 150 nm. Further, second address informationindicative of an end position of the blank region 12 is recorded on thecontent region 13. A track pitch in the content region 13 is 320 nmwhich is smaller than that in the medium information region 11.

In a case where such address information indicative of location of theblank region 12 is recorded, the reproduction device (i) can recognizethe location of the blank region 12 so as to carry out proper processing(e.g. change laser beam power of the reproduction device) with respectto the blank region 12 and the content region 13, and (ii) can cause theoptical system to consecutively jump to an adjacent track in the blankregion 12 so as to smoothly shift to reproduction of the content region13 in a relatively short time period.

FIG. 8 is a cross-sectional view of the super-resolution medium 20.

The super-resolution medium 20 is arranged such that (i) a reflectinglayer 16 and a super-resolution function layer 17 which causes asuper-resolution effect are stacked in this order by sputtering on asubstrate 15 on which the prepits of each of the regions are provided,and (ii) a substrate 18 having translucency is provided on thesuper-resolution function layer 17.

The substrate 15 has a thickness of approximately 0.6 mm, and is made ofpolycarbonate. The reflecting layer 16 is a silicon layer having athickness of 7 nm, and the super-resolution function layer 17 is a zincoxide layer having a thickness of 155 nm. The substrate 18 has athickness of approximately 0.6 mm, and is made of polycarbonate. Notethat the prepits of each of the regions are provided on the substrate 15so as to have concave shape and/or convex shape.

In a case where the content region 13 is irradiated by a laser beamhaving power suitable for reproduction of the content region 13, heat isgenerated by the reflecting layer 16. The heat causes a light intensitydistribution within a laser spot, which distribution causes temperaturedistribution. This ultimately causes optical transmittance distributionwithin the laser spot on the super-resolution function layer 17. As aresult, the laser spot goes into a pseudo-reduction state. This allows areproduction of the train of prepits in the content region 13 whichtrain of prepits includes prepits shorter than the resolution limit ofthe optical system of the reproduction device, thereby making itpossible to deal with more information than a normal medium. Note thatthe super-resolution function layer 17 is not limited to a specificstructure, provided that the train of prepits in the content region 13can be reproduced. The super-resolution function layer 17 can be a masklayer disclosed in Patent Literature 1 or a function layer disclosed inPatent Literature 2, for example.

Further, the medium identification information recorded on the mediuminformation region 11 can be reproduced with the use of a laser beamhaving power suitable for a normal medium. This is because the mediumidentification information is recorded with the use of a train ofprepits which is constituted by prepits longer than the resolution limitof the optical system of the reproduction device, i.e., the mediumidentification information is recorded in a similar manner to a normalmedium. Therefore, the reproduction device (i) irradiates a medium,which is loaded into the reproduction device, with a laser beam havingpower for a normal medium so as to read out the medium identificationinformation, and then (ii) determines, based on the mediumidentification information, whether the medium thus loaded is a normalmedium or a super-resolution medium. Based on a result thus determined,the reproduction device can carry out processing in accordance with themedium thus loaded (can change, for example, the power of a laser beamin accordance with the medium thus loaded). This allows realization of acompatible reproduction device that is capable of reproducing both of anormal medium and the super-resolution medium 20. Note that laser beampower suitable for reproduction of the medium information region 11 isapproximately 0.3 mW which is the same as laser beam power suitable forreproduction of a normal medium.

The following description deals with the blank region 12 in more detailwith reference to FIG. 7. Note that, for convenience of description, atrain of prepits in the medium information region 11 which train ofprepits is adjacent to the blank region 12 is hereinafter referred to as“a train of prepits c”, and a train of prepits in the content region 13which train of prepits is adjacent to the blank region 12 is hereinafterreferred to as “a train of prepits d”. Further, of the four trains ofprepits in the blank region 12, a train of prepits that is adjacent tothe train of prepits c in the medium information region 11 ishereinafter referred to as “a train of prepits K”, and a train ofprepits that is adjacent to the train of prepits K and nearer to thecontent region 13 than the train of prepits c is hereinafter referred toas “a train of prepits L”. Further, a train of prepits that is adjacentto the train of prepits L and is nearer to the content region 13 thanthe train of prepits K is hereinafter referred to as “a train of prepitsM”, and a train of prepits that is adjacent to the train of prepits Mand the train of prepits d is hereinafter referred to as “a train ofprepits N”.

The train of prepits K in the blank region 12 is provided so as to beaway, by a track pitch of 400 nm (by a track pitch of the mediuminformation region 11), from the adjacent train of prepits c. A trackpitch between the trains of prepits K and L is smaller by approximately20 nm than that between the trains of prepits c and K, and a track pitchbetween the trains of prepits L and M is smaller by approximately 20 nmthan that between the trains of prepits K and L, and a track pitchbetween the trains of prepits M and N is smaller by approximately 20 nmthan that between the trains of prepits L and M. Consequently, the trainof prepits N is provided so as to be away, by a track pitch ofapproximately 320 nm, from the adjacent train of prepits M. Further, thetrain of prepits N is provided so as to be away, by a track pitch of 320nm, from the adjacent train of prepits d.

As in the Embodiments 1 through 3, the blank region 12 provided in thismanner allows proper reproduction of the medium information region 11and the content region 13 without causing an increase in reproductionerror, although the medium information region 11 and the content region13 are different in recording mode and track pitch. This allows thesuper-resolution medium 20 to have larger storage capacity than a normalmedium, and to be reproduced in a single reproduction device which canreproduce a normal medium.

Further, since the four guide grooves are provided in the blank region12, the blank region 12 has a large area. Because of this, there is norapid change in track pitch. This makes it possible to easily control aspeed at which a slider is moved during manufacturing of a master disc.Further, the reproduction device can carry out tracking servo controlmore stably while causing the optical system to travel through the blankregion 12. This allows an increase in margin for external disturbancesand the like, thereby allowing the optical system to more smoothly movefrom the medium information region 11 to the content region 13.

In a case where it is desired that storage capacity be secured as muchas possible in a super-resolution medium, it is only necessary to makethe blank region 12 as small as possible, for example, by causing thetrain of prepits in the blank region 12 to go around twice as in theEmbodiment 1. Further, at a certain position in a circumferentialdirection, a track pitch between a train of prepits or a guide grooveand an adjacent train of prepits or guide groove on the innercircumferential side may become smaller as a distance from an innerperiphery becomes larger. Specifically, such a track pitch may becomesmaller as follows as a distance from an inner periphery becomes larger:400 nm, approximately 385 nm, approximately 360 nm, approximately 330nm, approximately 325 nm, 320 nm. This makes it easier to manufacture amaster disc of an optical recording medium. Specifically, in a casewhere an amount of change in speed at which a slider is moved in aradial direction of the master disc becomes smaller from a certain pointas above, the speed at which the slider is moved tends to become stablewhen a track pitch between a train of prepits or a guide groove and anadjacent train of prepits or guide groove on the inner circumferentialside is 320 nm.

The super-resolution medium 20 thus described is a suitable example, andcan be modified as follows, for example.

The reflecting layer 16 can be made of any material, provided thatsufficient amount of reflection can be obtained. The super-resolutionfunction layer 17 can be made of a material such as CeO₂, TiO₂, GeSbTeor AgInSbTe, for example. The substrate 18 can be prepared by a methodsuch as a method of bonding a film with the use of a UV cured resin orby a spin coat method.

Further, the blank region 12 is not limited in particular, provided that(i) the optical system of the reproduction device can move whilecarrying out tracking, and (ii) the blank region 12 includes a prepit ofnot less than the shortest prepit of the trains of prepits in thecontent region 13. Further, the train of prepits in the blank region 12may be substituted by the guide groove of the Embodiment 2 which guidegroove spirally goes around at least twice or the combination of trainof prepits and guide groove of the Embodiment 3 which train of prepitsand guide groove spirally go around at least twice. A depth of each ofthe guide grooves is not limited to a specific one, provided that such adepth allows the optical system of the reproduction device to detect atracking error signal. A depth of approximately 40 nm causes no problemin a case where the optical system is set as described in the presentembodiment. Further, the train of prepits or the combination of train ofprepits and guide grooves in the blank region 12 can be not less thantwo types of prepits, having respective different lengths, which arerandomly provided so as not to comply with any signal modulation methodof an optical recording medium. This is because no information to bereproduced such as medium information or content information is recordedon the blank region 2.

Further, the present embodiment has dealt with an arrangement in whichthe address information of the blank region 12 is recorded on each ofthe medium information region 11 and the content region 13, but does notintent to limit to this. Alternatively, the address information of theblank region 12 may be recorded on the medium information region 11 in adifferent information state.

The medium information region 11 may contain, instead of the addressinformation of the blank region 12, address information indicative oflocation of the content region 13. In a case where the addressinformation of the content region 13 is recorded on the mediuminformation region 11, the reproduction device (i) can recognize thelocation of the blank region 12 and the content region 13 so as to carryout proper processing (e.g. change laser beam power of the reproductiondevice) with respect to the blank region 12 and the content region 13,and (ii) can cause the optical system to consecutively jump to anadjacent track in the blank region 12 so as to speedily access astarting position or a desired position of the content region 13 andsmoothly shift to reproduction of the content region 13 in a relativelyshort time period.

The present embodiment has dealt with a case where the mediuminformation region 11 includes the test read region 11A. However,another arrangement is possible in which (i) the medium informationregion 11 includes, instead of the test read region 11A, a region, onwhich power information indicative of power of a laser beam with whichthe content region 13 is irradiated, is recorded, and (ii) thereproduction device reproduces the power information so as to recognizepower of a laser beam suitable for reproduction of the content region13. The test read region 11A may be substituted by the test read region1A of the Embodiment 1. Further, in a case where a plurality ofsuper-resolution media are the same in laser beam power suitable forreproduction of the content region, such laser beam power can berecorded in the reproduction device instead of providing the test readregion 11A.

The medium information region 11 may contain blank power informationindicative of power of a laser beam with which the blank region 12 isirradiated. The reproduction device reproduces the blank powerinformation so as to recognize laser beam power suitable for the blankregion 12. Note that the laser beam power suitable for the blank region12 may be smaller than that suitable for reproduction of the contentregion 13. In such a case, it is possible to reduce power consumption ofthe reproduction device since the reproduction device can accuratelyrecognize the laser beam power suitable for the blank region 12 based onthe blank power information.

Each of the Embodiments 1 through 4 has discussed super-resolution mediasuch as BD-ROM (Blu-ray Disc Read Only Memory), BD-R (Blu-ray DiscRecordable), BD-RE (Blu-ray Disc Rewritable) and HD_DVD. However, asuper-resolution medium of the present invention is also applicable toCD-ROM (Compact Disc Read Only Memory), CD-R (Compact Disc Recordable),CD-RW (Compact Disc Rewritable), DVD-ROM (Digital Versatile Disc ReadOnly Memory), DVD-R (Digital Versatile Disc Recordable), and DVD-RW(Digital Versatile Disc Rewritable).

Embodiment 5

An embodiment of a reproduction device of the present invention isdescribed below with reference to FIGS. 9 through 11. The presentembodiment discusses, as examples, (i) a case where a normal medium isreproduced with the use of a reproduction device 50 of the presentembodiment and (ii) a case where the super-resolution medium 10 a of theEmbodiment 2 is reproduced with the use of the reproduction device 50 ofthe present embodiment.

FIG. 9 is a view illustrating an arrangement of the reproduction device50.

As shown in FIG. 9, the reproduction device 50 includes a spindle motor22, an optical pickup (reproducing section) 26, an optical pickup motor27, a head amplifier 28, a control section 36, a servo control section37, a laser control section 38, and an RF signal processing section 39.Note that a normal medium or the super-resolution medium 10 a is loaded,as an optical recording medium 21, into the reproduction device 50.

The spindle motor 22 rotates the optical recording medium 21 in orderthat information recorded on the optical recording medium 21 isreproduced.

The optical pickup 26 includes a converging lens (not shown), adiffraction grating (not shown), a ¼ wave plate (not shown), a polarizedbeam splitter 23, a laser light source 24, and a photodetector 25.

The laser light source 24 emits a laser beam in order that theinformation recorded on the optical recording medium 21 is reproduced.The laser beam emitted from the laser light source 24 has a wavelengthof 405 nm as described in the Embodiment 2. The laser light source 24emits a laser beam having power suitable for a normal medium at aninitial stage of reproduction. The diffraction grating causes the laserbeam emitted from the laser light source 24 to be separated into a mainbeam for signal reproduction and a sub beam for tracking servo (the mainbeam and the sub beam are hereinafter collectively referred to simply as“laser beam”).

The polarized beam splitter 23 allows transmission of the laser beam orreflects the laser beam in accordance with a polarization direction ofthe laser beam. The polarized beam splitter 23 reflects a laser beamwhich has passed through the diffraction grating. The ¼ wave plate iscapable of converting linear polarization into circular polarization orconverting circular polarization into linear polarization. The ¼ waveplate converts the laser beam reflected from the polarized beam splitter23 into circularly polarized light. The converging lens causes the laserbeam which has passed through the ¼ wave plate to be focused on theoptical information recording medium 21. The numerical aperture NA ofthe converging lens is 0.85 as described in the Embodiment 2.

The laser beam reflected from the optical recording medium 21 passesthrough the converging lens, is converted into linearly polarized lightby the ¼ wave plate, passes through the polarized beam splitter 23, andis then applied to the photodetector 25. The photodetector 25 convertsthe light reflected from the optical recording medium 21 into anelectric signal.

The optical pickup motor 27 controls location of the optical pickup 26under the control of the control section 36 so that the optical pickup26 accesses a desired position of the optical information recordingmedium 21.

The head amplifier 28 amplifies the electric signal generated in thephotodetector 25.

The control section 36 controls operation of the reproduction device 50.This is described below in detail.

The servo control section 37 carries out various kind of general servocontrol such as tracking servo control based on the electric signalamplified by the head amplifier 28. For example, the tracking servocontrol is such that (i) a tracking error signal is generated from theelectric signal amplified by the head amplifier 28, and (ii) theconverging lens in the optical pickup 26 is repeatedly controlled untila value of a tracking error signal becomes zero.

The laser control section 38 controls power of a laser beam emitted fromthe laser light source 24, by a general method under the control of thecontrol section 36.

The RF signal processing section 39 includes an RF amplifier 39A and anRF signal processing circuit (content information reproducing section)39B. The RF amplifier 39A further amplifies the electric signalamplified by the head amplifier 28. Under the control of the controlsection 36, the RF signal processing circuit 39B carries outequalization process and decoding process with respect to the electricsignal amplified by the RF amplifier 39A so as to reproduce contentinformation recorded on the optical recording medium 21. The term“equalization process” refers to an arithmetic process for reducingsignal distortion and noise caused by an adjacent prepit, an adjacentspace and the like, and the term “decoding process” refers to anarithmetic process for decoding a waveform of a signal that has beensubjected to the equalization process so as to convert it into a digitalsignal represented by “1” or “0”. Note that the RF signal processingcircuit 39B does not carry out the equalization process and the decodingprocess at an initial stage of reproduction. Note also that the term“initial stage of reproduction” basically refers to “stage ofreproduction of the medium information region”.

FIG. 10 illustrates an arrangement of the control section 36.

As shown in FIG. 10, the control section 36 includes an access positioncontrol section 30, a signal processing section (information acquisitionsection) 31, a medium identification section 32, a power control section33, a reproduction clock control section 34, and an RF processingcontrol section (blank control section) 35.

The access position control section 30 controls the optical pickup motor27 so that the optical pickup 26 accesses a desired position of theoptical recording medium 21. At the start of reproduction, the accessposition control section 30 controls the optical pickup motor 27 so thatthe optical pickup 26 accesses the medium information region of theoptical recording medium 21.

The signal processing section 31 carries out equalization process anddecoding process with respect to the electric signal supplied from thehead amplifier 28 so as to reproduce various kinds of information. Thesignal processing section 31 supplies the various kinds of informationto the medium identification section 32, the power control section 33,the reproduction clock control section 34, and the RF processing controlsection 35.

The medium identification section 32 is provided in the signalprocessing section 31, and determines, based on the information (mediumidentification information) supplied from the signal processing section31, whether the optical recording medium 21 is a normal medium or thesuper-resolution medium 10 a.

The power control section 33 controls the laser control circuit 38 basedon the information supplied from the signal processing section 31 so asto control power of a laser beam emitted from the laser light source 24.

The reproduction clock control section 34 controls, based on theinformation (reproduction clock switching information) supplied from thesignal processing section 31, a reproduction clock used while thecontent information is being reproduced by the RF signal processingcircuit 39B.

The RF processing section 35 controls the equalization process and thedecoding process carried out in the RF signal processing circuit 39B,based on a result determined by the medium identification section 32 orthe information (address information (blank region information) of theblank region 2 a) supplied from the signal processing section 31.

The following description deals with processing operation (reproductionoperation) of the reproduction device 50 with reference to FIG. 11. FIG.11 shows a flow of the processing operation of the reproduction device50.

When the optical recording medium 21 is loaded into the reproductiondevice 50, the reproduction device 50 detects the optical recordingmedium 21 and causes the spindle motor 22 to rotate the opticalrecording medium 21 (“START” in the flow chart of FIG. 11). Next, theaccess position control section 30 of the control section 36 controlsthe optical pickup motor 27 so that the optical pickup 26 accesses themedium information region of the optical recording medium 21. Note that,at the start of the reproduction, the optical pickup accesses the mediuminformation region. Subsequently, the medium information region isirradiated with a laser beam emitted from the laser light source 24 (S1in the flow chart of FIG. 11). The laser beam emitted from the laserlight source 24 has power suitable for a normal medium. Note that, atthe start of the reproduction, the laser light source 24 emits a laserbeam having power suitable for a normal medium.

The light reflected from the medium information region is supplied tothe photodetector 25 via the polarized beam splitter 23, and thephotodetector 25 converts the light into an electric signal. Theelectric signal generated in the photodetector 25 is supplied to thesignal processing section 31 of the control section 36, the servocontrol section 37, and the RF processing section 39 via the headamplifier 28. The servo control section 37 carries out various kinds ofservo control in response to the electric signal. The RF signalprocessing circuit 39B carries out no processing since this is theinitial stage of the reproduction.

The signal processing section 31 processes the electric signal so as toreproduce the medium identification information (S2), and supplies themedium identification information to the medium identification section32. The medium identification section 32 identifies the opticalrecording medium 21 based on the medium identification information (S3).

In a case where it is determined, by the medium identification section32, that the optical recording medium is a normal medium (“NO” in S3),the RF processing control section 35 controls the RF signal processingcircuit 39B based on the result determined by the medium identificationsection 32 so that the RF signal processing circuit 39B carries outequalization process and decoding process (S8). Next, the optical pickup26 is caused access a content region of the normal medium, and the laserlight source 24 irradiates the content region with a laser beam havingpower suitable for a normal medium (S9). The laser beam reflected fromthe content region is supplied to the RF signal processing section 39via the photodetector 25 and the head amplifier 28, and the RF signalprocessing section 39 reproduces content information (S10).

Meanwhile, in a case where it is determined, by the mediumidentification section 32, that the optical recording medium 21 is thesuper-resolution medium 10 a (“YES” in S3), the optical pickup 26 iscaused to access the test read region 1B of the medium informationregion 1 a, and the laser light source 24 irradiates the test readregion 1B with a laser beam. The laser beam is reflected from the testread region 1B, and is supplied to the power control section 33 via thephotodetector 25, the head amplifier 28, and the signal processingsection 31. The power control section 33 controls the laser controlcircuit 38 so as to gradually change power of the laser beam emittedfrom the laser light source 24. Thus, the power control section 33determines laser beam power suitable for the blank region 2 a and thecontent region 3 a (S4).

More specifically, the power control section 33 reproduces the train ofprepits in the test read region 1A which train of prepits has a lengthequivalent to reference data while changing power of the laser beamemitted from the laser light source 24, and determines laser beam powerwhich causes the smallest number of reproduction errors, as the laserbeam power suitable for the blank region 2 a and the content region 3 a.However, the present embodiment is not limited to this. Alternatively,the power control section 33 may determine, as the laser beam powersuitable for the blank region 2 a and the content region 3 a, laser beampower which makes a tilt margin of the medium maximum or a middle valueof values of laser beam power which causes an error at a rate equal toor smaller than a predetermined rate. The power control section 33stores, in a memory (not shown), the laser beam power suitable for theblank region 2 a and the content region 3 a.

Subsequently, the reproduction clock switching information recorded onthe medium information region 1 a is reproduced by the signal processingsection 31, and is then supplied to the reproduction clock controlsection 34. Based on the reproduction clock switching information, thereproduction clock control section 34 controls the reproduction clockused while the content information is being reproduced by the RF signalprocessing circuit 39B so as to switch the reproduction clock into theone suitable for a super-resolution medium (S5).

Subsequently, the address information of the blank region 2 a that isrecorded on the medium information region 1 a is reproduced by thesignal processing section 31, and is then supplied to the power controlsection 33 and the RF processing control section 35. Based on theaddress information of the blank region 2 a, the power control section33 changes power of the laser beam emitted from the laser light source24 into the one determined in S4, i.e., the one suitable for the contentregion 3 a. Further, based on the address information of the blankregion 2 a, the RF processing control section 35 causes the RF signalprocessing circuit 39B to maintain its state, i.e., stop theequalization process and the decoding process (S6).

When the optical pickup 26 moves from the medium information region 1 ato the blank region 2 a, light reflected from the blank region 2 a issupplied to the servo control section 37 via the photodetector 25 andthe head amplifier 28 so that the various kinds of servo control arecontinued (S7). Since no information is recorded on the blank region 2a, reproduction of the blank region 2 a does not affect the control ofthe control section 36.

Subsequently, the optical pickup 26 moves from the blank region 2 a tothe content region 3 a. In this case, the power control section 33maintains the power of the laser beam emitted from the laser lightsource 24 based on the address information of the blank region 2 a.Further, the RF processing control section 35 controls the RF signalprocessing circuit 39B based on the address information of the blankregion 2 a so that the RF signal processing circuit 39B carries out theequalization process and the decoding process (S8).

When the optical pickup 26 moves from the blank region 2 a to thecontent region 3 a, light reflected from the content region 3 a issupplied to the RF signal processing section 39 via the photodetector 25and the head amplifier 28 so that content information is reproduced(S10).

As described above, the reproduction device 50 reproduces the mediumidentification information with the use of a laser beam having powersuitable for a normal medium, and then determines, based on the mediumidentification information thus reproduced, whether an loaded opticalrecording medium is a normal medium or the super-resolution medium 10 a.Based on a result thus determined, the reproduction device 50 carriesout processing suitable for the type of the optical recording medium(emits a laser beam having power suitable for the type of the opticalrecording medium). In the blank region 2 a, the reproduction device 50continues to carry out the servo control, but stops the equalizationprocess and the decoding process so as to stop the reproduction of thecontent information. In this manner, the reproduction device 50 iscapable of reproducing both of a normal medium and the super-resolutionmedium 10 a.

Further, it is possible to reduce power consumption of the reproductiondevice 50 since the reproduction device 50 does not carry out theequalization process and the decoding while causing the optical systemto travel through the blank region 2 a, as described above. Further, itis possible to shorten a time period it takes for the optical system totravel through the blank region 2 a in a case where the reproductiondevice 50 is arranged such that linear speed, which is traveling speedof the optical system in a tangential direction, is controlled by theequalization process and/or the decoding process. This makes it possibleto more smoothly shift to reproduction of the content region 3 a in ashorter time after the reproduction of the medium information region 1a.

The present embodiment has dealt with a case where the test read region1A is used in determining laser beam power suitable for reproduction ofthe content region 3 a. However, in a case where a plurality ofsuper-resolution media are the same in laser beam power suitable forreproduction of the content region, information of such laser beam powermay be recorded in the reproduction device 50 and the most suitablelaser beam power may be determined based on the information. It is alsopossible that information of laser beam power determined with the use ofthe test read region is recorded in a memory, and next time the mostsuitable laser beam power is determined based on the information.

Embodiment 6

Another embodiment of a reproduction device of the present invention isdescribed below with reference to FIG. 12. The present embodiment dealswith, as examples, a case where a reproduction device 50 a reproduces anormal medium and a case where the reproduction device 50 a reproducesthe super-resolution medium 10 b described in the Embodiment 3. Forconvenience of description, constituents which have identical functionsto those of the Embodiment 5 are given identical reference numerals, andare not explained repeatedly. Basically, the following description dealswith differences from the reproduction device 50 of the Embodiment 5.

An arrangement of the reproduction device 50 a is similar to that of thereproduction device 50, and therefore is not described here.

The following description deals with processing operation (reproductionoperation) of the reproduction device 50 a with reference to FIG. 12.FIG. 12 shows a flow of the processing operation of the reproductiondevice 50 a. The processing operation of the reproduction device 50 a isdifferent from that of the reproduction device 50 (see FIG. 11) in that(i) “S4A” is added between “S4” and “S5”, (ii) “S6” is replaced by“S6A”, and (iii) “S7A” is added between “S7” and “S8”.

When an optical recording medium 21 is loaded into the reproductiondevice 50 a, the reproduction device 50 a detects the optical recordingmedium 21 and causes a spindle motor 22 to rotate the optical recordingmedium 21 (“START” in the flow chart of FIG. 12). Next, an accessposition control section 30 of a control section 36 controls an opticalpickup motor 27 so that an optical pickup 26 accesses a mediuminformation region of the optical recording medium 21. Note that, at thestart of the reproduction, the optical pickup accesses the mediuminformation region. Subsequently, the medium information region isirradiated with a laser beam emitted from a laser light source 24 (S1 inthe flow chart of FIG. 12). The laser beam emitted from the laser lightsource 24 has power suitable for a normal medium. Note that, at thestart of the reproduction, the laser light source 24 emits a laser beamhaving power suitable for a normal medium.

The light reflected from the medium information region is supplied to aphotodetector 25 via various kinds of lens and a polarized beam splitter23, and the photodetector 25 converts the light into an electric signal.The electric signal generated in the photodetector 25 is supplied to asignal processing section 31 of the control section 36, a servo controlsection 37, and an RF processing section 39 via a head amplifier 28. Theservo control section 37 carries out various kinds of servo control inresponse to the electric signal. An RF signal processing circuit 39Bcarries out no processing since this is the initial stage of thereproduction. The signal processing section 31 processes the electricsignal so as to reproduce the medium identification information (S2),and supplies the medium identification information to a mediumidentification section 32. The medium identification section 32identifies the optical recording medium 21 based on the mediumidentification information (S3).

In a case where it is determined, by the medium identification section32, that the optical recording medium is a normal medium (“NO” in S3),the RF processing control section 35 controls the RF signal processingcircuit 39B based on the result determined by the medium identificationsection 32 so that the RF signal processing circuit 39B carries outequalization process and decoding process (S8). Next, the optical pickup26 is caused access a content region of the normal medium, and the laserlight source 24 irradiates the content region with a laser beam havingpower suitable for a normal medium (S9). The laser beam reflected fromthe content region is supplied to the RF signal processing section 39via the photodetector 25 and the head amplifier 28, and the RF signalprocessing section 39 reproduces content information (S10).

Meanwhile, in a case where it is determined, by the mediumidentification section 32, that the optical recording medium 21 is thesuper-resolution medium 10 b (“YES” in S3), the optical pickup 26 iscaused to access the test read region 1B of the medium informationregion 1 b, and the laser light source 24 irradiates the test readregion 1B with a laser beam. The laser beam is reflected from the testread region 1B, and is supplied to the power control section 33 via thephotodetector 25, the head amplifier 28, and the signal processingsection 31. The power control section 33 controls the laser controlcircuit 38 so as to gradually change power of the laser beam emittedfrom the laser light source 24. Thus, the power control section 33determines laser beam power suitable for the content region 3 b (S4).

More specifically, the power control section 33 reproduces the train ofprepits in the test read region 1B which train of prepits has a lengthequivalent to reference data while changing power of the laser beamemitted from the laser light source 24, and determines laser beam powerwhich causes the smallest number of reproduction errors, as the laserbeam power suitable for the content region 3 b. However, the presentembodiment is not limited to this. Alternatively, the power controlsection 33 may determine, as the laser beam power suitable for thecontent region 3 b, laser beam power which makes a tilt margin of themedium maximum or a middle value of values of laser beam power whichcauses an error at a rate equal to or smaller than a predetermined rate.The power control section 33 stores, in a memory (not shown), the laserbeam power suitable for the content region 3 b.

Subsequently, the blank power information recorded on the mediuminformation region 1 b is reproduced by the signal processing section 31so that laser beam power suitable for the blank region 2 b isdetermined. The power control section 33 stores, in the memory (notshown), the laser beam power suitable for the blank region 2 b (S4A).Subsequently, the reproduction clock switching information recorded onthe medium information region 1 b is reproduced by the signal processingsection 31, and is then supplied to the reproduction clock controlsection 34. Based on the reproduction clock switching information, thereproduction clock control section 34 controls the reproduction clockused while the content information is being reproduced by the RF signalprocessing circuit 39B so as to switch the reproduction clock into theone suitable for a super-resolution medium (S5).

Subsequently, the address information of the blank region 2 b that isrecorded on the medium information region 1 b is reproduced by thesignal processing section 31, and is then supplied to the power controlsection 33 and the RF processing control section 35. Based on theaddress information of the blank region 2 b, the power control section33 changes power of the laser beam emitted from the laser light source24 into the one determined in S4A, i.e., the one suitable for the blankregion 2 b. Further, based on the address information of the blankregion 2 b, the RF processing control section 35 causes the RF signalprocessing circuit 39B to maintain its state, i.e., stop theequalization process and the decoding process (S6A).

When the optical pickup 26 moves from the medium information region 1 bto the blank region 2 b, light reflected from the blank region 2 b issupplied to the servo control section 37 via the photodetector 25 andthe head amplifier 28 so that the various kinds of servo control arecontinued (S7). Since no information is recorded on the blank region 2b, reproduction of the blank region 2 b does not affect the control ofthe control section 36.

Next, the optical pickup 26 moves from the blank region 2 b to thecontent region 3 b. In this case, based on the address information ofthe blank region 2 b, the power control section 33 changes power of thelaser beam emitted from the laser light source 24 into the onedetermined in S4, i.e., the one suitable for the content region 3 b(S7A). Further, the RF processing control section 35 controls the RFsignal processing circuit 39B based on the address information of theblank region 2 b so that the RF signal processing circuit 39B carriesout the equalization process and the decoding process (S8).

When the optical pickup 26 moves from the blank region 2 b to thecontent region 3 b, light reflected from the content region 3 b issupplied to the RF signal processing section 39 via the photodetector 25and the head amplifier 28 so that content information is reproduced(S10).

As described above, the reproduction device 50 a reproduces the mediumidentification information with the use of a laser beam having powersuitable for a normal medium, and then determines, based on the mediumidentification information thus reproduced, whether an loaded opticalrecording medium is a normal medium or the super-resolution medium 10 b.Based on a result thus determined, the reproduction device 50 a carriesout processing suitable for the type of the optical recording medium(emits a laser beam having power suitable for the type of the opticalrecording medium). In the blank region 2 b, the reproduction device 50 acontinues to carry out the servo control, but stops the equalizationprocess and the decoding process so as to stop the reproduction of thecontent information. In this manner, the reproduction device 50 a iscapable of reproducing both of a normal medium and the super-resolutionmedium 10 b.

Further, it is possible to reduce power consumption of the reproductiondevice 50 a since the reproduction device 50 a does not carry out theequalization process and the decoding while causing the optical systemto travel through the blank region 2 b, as described above. Further, itis possible to shorten a time period it takes for the optical system totravel through the blank region 2 b in a case where the reproductiondevice 50 a is arranged such that linear speed, which is traveling speedof the optical system in a tangential direction, is controlled by theequalization process and/or the decoding process. This makes it possibleto more smoothly shift to reproduction of the content region 3 b in ashorter time after the reproduction of the medium information region 1b.

The present embodiment has dealt with a case where the test read region1B is used in determining laser beam power suitable for reproduction ofthe content region 3 b. However, in a case where a plurality ofsuper-resolution media are the same in laser beam power suitable forreproduction of the content region, information of such laser beam powermay be recorded in the reproduction device 50 a and the most suitablelaser beam power may be determined based on the information. It is alsopossible that information of laser beam power determined with the use ofthe test read region is recorded in a memory, and next time the mostsuitable laser beam power is determined based on the information.

The Embodiments 5 and 6 dealt with how the super-resolution medium 10 aand the super-resolution medium 10 b are reproduced, respectively. Thefollowing description deals with how the super-resolution medium 10described in the Embodiment 1 is reproduced. The super-resolution medium10 is reproduced as follows, for example.

After completion of reproduction of the medium information region 1, theblank region 2 is reproduced without changing laser beam power (sincethe address information of the blank region 2 is not recorded). In thiscase, a spot diameter does not go into a pseudo-reduction state sincethe laser beam power is not changed. Therefore, the tracking servocontrol is not carried out properly as a track pitch becomes narrower.The servo control section 37 detects such improper tracking servocontrol, and then supplies the information (blank region information) tothe signal processing section 31. Based on the information, the laserbeam power is changed into the one suitable for the content region 3,and reproduction is continued (reproduction shifts from the blank region2 to the content region 3). Note that the servo control section 37 candetect such improper tracking servo control by detecting a state wherestable control (i.e., a state where a value of a tracking error signalbecomes zero) is not achieved due to disturbances such as noise from anadjacent track (e.g., a state where a value of a tracking error signalis not zero continues for over a certain period of time).

Further, the super-resolution medium 20 of the Embodiment 4 which isoperated in conformity with the HD_DVD standard can be reproduced by asimilar method to the super-resolution mediums 10 a and 10 brespectively described in the Embodiments 5 and 6 in a case where theconverging lens is changed into the one having numerical aperture of0.65.

The arrangements of the reproduction devices 50 and 50 a respectivelydescribed in the Embodiments 5 and 6 are examples, and can be variedappropriately. For example, each of the reproduction devices 50 and 50 ais arranged such that the information of the medium information regionis reproduced in the signal processing section 31. However, anotherarrangement is possible in which the information of the mediuminformation region is reproduced in the RF signal processing circuit39B, and is then supplied to the signal processing section 31. Further,a tracking error signal may be generated in the signal processingsection 31, and a function of the servo control section 37 may besubstituted by the control section 36.

Finally, each of the sections of the control section 36 in each of thereproduction devices 50 and 50 a may be realized by way of hardware orsoftware as executed by a CPU as follows.

The reproduction devices 50 and 50 a each include a CPU (centralprocessing unit) and memory devices (memory media). The CPU (centralprocessing unit) executes instructions in control programs realizing thefunctions. The memory devices include a ROM (read only memory) whichcontains programs, a RAM (random access memory) to which the programsare loaded, and a memory containing the programs and various data. Theobjective of the present invention can also be achieved by mounting tothe reproduction devices 50 and 50 a a computer-readable storage mediumcontaining control program code (executable program, intermediate codeprogram, or source program) for the control section 36 of thereproduction devices 50 and 50 a, which is software realizing theaforementioned functions, in order for the computer (or CPU, MPU) toretrieve and execute the program code contained in the storage medium.

The storage medium may be, for example, a tape, such as a magnetic tapeor a cassette tape; a magnetic disk, such as a floppy (RegisteredTrademark) disk or a hard disk, or an optical disk, such asCD-ROM/MO/MD/DVD/CD-R; a card, such as an IC card (memory card) or anoptical card; or a semiconductor memory, such as a maskROM/EPROM/EEPROM/flash ROM.

The reproduction devices 50 and 50 a may be arranged to be connectableto a communications network so that the program code may be deliveredover the communications network. The communications network is notlimited in any particular manner, and may be, for example, the Internet,an intranet, extranet, LAN, ISDN, VAN, CATV communications network,virtual dedicated network (virtual private network), telephone linenetwork, mobile communications network, or satellite communicationsnetwork. The transfer medium which makes up the communications networkis not limited in any particular manner, and may be, for example, wiredline, such as IEEE 1394, USB, electric power line, cable TV line,telephone line, or ADSL line; or wireless, such as infrared radiation(IrDA, remote control), Bluetooth, 802.11 wireless, HDR, mobiletelephone network, satellite line, or terrestrial digital network. Thepresent invention encompasses a computer data signal embedded in acarrier wave in which the program code is embodied electronically.

Further, each of the reproduction devices may be stationary or portable.

The present invention is not limited to the description of theembodiments above, but may be altered by a skilled person within thescope of the claims. An embodiment based on a proper combination oftechnical means disclosed in different embodiments is encompassed in thetechnical scope of the present invention.

INDUSTRIAL APPLICABILITY

An optical recording medium of the present invention is applicable to amedium such as BD-ROM (Blu-ray Disc Read Only Memory), BD-R (Blu-rayDisc Recordable), BD-RE (Blu-ray Disc Rewritable), HD_DVD, CD-ROM(Compact Disc Read Only Memory), CD-R (Compact Disc Recordable), CD-RW(Compact Disc Rewritable), DVD-ROM (Digital Versatile Disc Read OnlyMemory), DVD-R (Digital Versatile Disc Recordable), or DVD-RW (DigitalVersatile Disc Rewritable).

The invention claimed is:
 1. An optical information recording mediumcomprising: a first region on which medium identification informationwhich causes a medium type to be identified is recorded with use ofguide grooves each of which has wobbles having a cycle longer than aresolution limit of an optical system of an optical recording mediumreproduction device; a second region on which content information is tobe recorded with use of trains of marks each of which includes a mark ora space equal to or shorter than the resolution limit of the opticalsystem, the second region having guide grooves having a track pitchsmaller than that of the first region, and the second region beingprovided outside an outer periphery of the first region; and a blankregion provided between the first region and the second region, theblank region having a first guide groove closest to the first region anda second guide groove closest to the second region, a track pitchbetween the first guide groove and an adjacent guide groove in a regionoutside the blank region being identical to the track pitch of the firstregion, a track pitch between the second guide groove and an adjacentguide groove in a region outside the blank region being identical to thetrack pitch of the second region, the blank region including at leasttwo tracks having a track pitch which changes from the track pitch ofthe first region to the track pitch of the second region, no informationbeing recorded on the blank region, and reproduction power informationfor reproducing the second region being recorded on the first region. 2.A method for reproducing the optical information recording medium as setforth in claim 1, the method comprising the steps of: acquiring thereproduction power information recorded on the first region; andreproducing the content information recorded on the second region.
 3. Anoptical information recording medium comprising: a first region on whichmedium identification information which causes a medium type to beidentified is recorded with use of trains of prepits each of which isconstituted by prepits longer than a resolution limit of an opticalsystem of an optical recording medium reproduction device; a secondregion on which content information is recorded with use of trains ofprepits each of which includes a prepit equal to or shorter than theresolution limit of the optical system, the second region having a trackpitch smaller than that of the first region; and a blank region providedbetween the first region and the second region so as to spirally connectthe trains of prepits in the first region and the trains of prepits inthe second region, the blank region including at least two trains ofprepits, a track pitch, between (i) a first one of said at least twotrains of prepits that is adjacent to a first one of the trains ofprepits of the first region and (ii) the first one of the trains ofprepits, being identical to a track pitch of the first region, a trackpitch, between (i) a second one of said at least two trains of prepitsthat is adjacent to a second one of the trains of prepits of the secondregion and (ii) the first one of the trains of prepits which is on thefirst region side, changing into a track pitch of the second region, anda track pitch, between (i) the second one of said at least two trains ofprepits and (ii) the second one of the trains of prepits being identicalto the track pitch of the second region, no information being recordedon the blank region, and reproduction power information for reproducingthe second region being recorded on the first region.
 4. A method forreproducing the optical information recording medium as set forth inclaim 3, the method comprising the steps of acquiring the reproductionpower information recorded on the first region; and reproducing thecontent information recorded on the second region.